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Randomized Controlled Trial
, 232 (12), 2031-42

Caffeine Improves Reaction Time, Vigilance and Logical Reasoning During Extended Periods With Restricted Opportunities for Sleep

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Randomized Controlled Trial

Caffeine Improves Reaction Time, Vigilance and Logical Reasoning During Extended Periods With Restricted Opportunities for Sleep

Gary H Kamimori et al. Psychopharmacology (Berl).

Abstract

Rationale: Various occupational groups are required to maintain optimal physical and cognitive function during overnight periods of wakefulness, often with less than optimal sleep. Strategies are required to help mitigate the impairments in cognitive function to help sustain workplace safety and productivity.

Objectives: To test the effectiveness of repeated 200 mg doses of caffeine on cognitive function and live-fire marksmanship with soldiers during three successive nights of sustained wakefulness followed by 4-h afternoon sleep periods.

Methods: Twenty Special Forces personnel (28.6 ± 4.7 years, 177.6 ± 7.5 cm and 81.2 ± 8.0 kg) were randomly assigned to receive four 200-mg doses of caffeine (n = 10) or placebo (n = 10) during the late evening and early morning hours during three successive days. An afternoon 4-h sleep period followed. The psychomotor (PVT) and field (FVT) vigilance, logical reasoning (LRT) tests and a vigilance monitor assessed cognitive function throughout the study. Live-fire marksmanship requiring friend-foe discrimination was assessed.

Results: Caffeine maintained speed on the PVT (p < 0.02), improved detection of events during FVT (p < 0.001), increased number of correct responses to stimuli as assessed by the vigilance monitor (p < 0.001) and increased response speed during the LRT (p < 0.001) throughout the three overnight testing periods. Live-fire marksmanship was not altered by caffeine.

Conclusions: A total daily dose of 800 mg caffeine during successive overnight periods of wakefulness is an effective strategy to maintain cognitive function when optimal sleep periods during the day are not available.

Figures

Fig. 1
Fig. 1
Response speed during the psychomotor vigilance test beginning during the evening of day 2 through to the morning of day 5 for the caffeine and placebo groups. The asterisk indicates a significant group by time interaction over the 3 days. The arrows indicate when 200 mg of caffeine or placebo was administered
Fig. 2
Fig. 2
The number of points recorded during the control (CTRL) and six field vigilance test (FVT) sessions for the caffeine and placebo groups. The asterisk indicates a significant main effect between groups throughout the overnight testing sessions, whereas the cross indicates that both groups performed worse during the second night of testing
Fig. 3
Fig. 3
The number of correct responses to the stimuli presented on the vigilance monitor during the control (CTRL) and six field vigilance test (FVT) sessions for the caffeine and placebo groups. The asterisk indicates a significant difference between groups during the given test session
Fig. 4
Fig. 4
Mean correct response time during the logical reasoning test beginning during the evening of day 2 through to the morning of day 5 for the caffeine and placebo groups. The asterisk indicates a significant difference between groups during the given test session

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